adhesive mark removal

["Erik Geerdink" <delorean502@xxxx>]

I have two adheasive marks on a left quarter panel I have (for 
sale). It looks like they have been there awhile. I tried using 
gas, but that didn't take it out (i didn't try to hard either). 
Should I try using gas again, or is there another product out there 
that will work better?
Thanks

Erik Geerdink